Deep‐red and, even more, near‐infrared (NIR) persistent emission from purely organic materials holds great potential for various photonic and optoelectronic devices. While a few deep‐red and NIR persistent emission systems have been reported using doping strategies, the concentrations of phosphorescent donor and fluorescent acceptor materials remain low for device applications. Here, a systematic photophysical study of selective donor–acceptor combinations based on triplet–singlet Förster‐resonance energy transfer (TS‐FRET) is presented. By codoping a donor with strong room‐temperature phosphorescence and a deep‐red fluorescent acceptor into an inert matrix, highly efficient persistent deep‐red emission is achieved, which is dominated by the acceptor with emission peaks at 596 and 648 nm. A phosphorescence quantum yield (QY) of up to 53.6% is obtained in films with 10 wt% donor concentration, and a remarkably high QY of 37.2% is maintained even at 30 wt%. The total photoluminescence QY increases from 75.2% to 85.7% as the donor concentration is raised from 2 to 20 wt%. This enhancement is attributed to efficient TS‐FRET, which effectively suppresses nonradiative losses. These findings highlight the potential of TS‐FRET for achieving efficient persistent deep‐red emission at elevated donor concentrations in purely organic systems.
Brillouin microscopy provides label‐free optical contrast related to the high‐frequency longitudinal mechanical response of materials, yet weak Brillouin signals and strong elastic background continue to limit measurement speed and precision, particularly under constrained optical exposure. Recent advances in optical instrumentation have improved the generation, discrimination, and detection of Brillouin signals. This review discusses these developments, focusing on the relationships among spectral precision, acquisition throughput, background rejection, and optical dose, as well as how different instrument architectures address specific measurement requirements and sample conditions. Emerging strategies based on optical‐field control, parallel acquisition, pulsed excitation, and compact photonic integration further illustrate how optical design can improve the efficiency, measurement capability, and robustness of Brillouin microscopy.
Solution‐processed semiconductors with tunable optical absorption and compatibility with complementary metal–oxide–semiconductor technology offer an attractive route for near‐infrared (NIR) photodetection. Colloidal quantum dots (CQDs) are promising candidates due to their solution processability and superior optoelectronic properties. Although CQD/Si heterojunction photodiodes extend the photoresponse of silicon beyond its intrinsic absorption limit, their photocurrent is typically limited, often requiring external operational amplifiers for signal readout. Here, we demonstrate a PbS CQD photodiode‐integrated silicon bipolar junction transistor (BJT) that enables intrinsic electrical amplification of the NIR photoresponse. Device simulations show that optical absorption in the CQD layer generates a photovoltage at the CQD/Si heterojunction, which drives the transistor into the active regime and produces an amplified collector voltage. Proof‐of‐concept experiments using PbS CQD/Si photodiodes coupled to a commercial npn BJT confirm current amplification and a linear dependence of the output voltage on the incident optical power.
In order to extract accurate information from a thermoluminescence glow curve it is necessary to correct it for thermal quenching. Assuming that the dominant quenching process is due to nonradiative deactivation, the correction can be made by the Mott–Seitz equation. However, the experimentally determined quenching curve from the temperature dependence of luminescence intensity or integrated band area often suffers from a pronounced “bump” which we associate with thermoluminescence. It is shown that good data fits can be achieved by employing the higher temperature region above thermoluminescence. For demonstration, the commercial persistent luminescence phosphor SrAl2O4:Eu2+, Dy3+ has been chosen. The thermal quenching parameter WTQ was found to be 5016 ± 121 cm−1 and the quenching mechanism was deduced to be ionization to the conduction band. The corrected glow curves have been analyzed by the Kitis and initial rise methods and indicate a continuous distribution of traps at ~4000–5000 cm−1 below the conduction band. These are normally taken to be oxygen vacancies together with the cooperation of dysprosium ions.
In order to extract accurate information from a thermoluminescence glow curve it is necessary to correct it for thermal quenching. Assuming that the dominant quenching process is due to nonradiative deactivation, the correction can be made by the Mott–Seitz equation. However, the experimentally determined quenching curve from the temperature dependence of luminescence intensity or integrated band area often suffers from a pronounced “bump” which we associate with thermoluminescence. It is shown that good data fits can be achieved by employing the higher temperature region above thermoluminescence. For demonstration, the commercial persistent luminescence phosphor SrAl 2 O 4 :Eu 2+ , Dy 3+ has been chosen. The thermal quenching parameter W TQ was found to be 5016 ± 121 cm −1 and the quenching mechanism was deduced to be ionization to the conduction band. The corrected glow curves have been analyzed by the Kitis and initial rise methods and indicate a continuous distribution of traps at ~4000–5000 cm −1 below the conduction band. These are normally taken to be oxygen vacancies together with the cooperation of dysprosium ions.
